pinctrl: mediatek: reuse pinctrl driver for mt7623

mt7623 pinctrl hardware can be compatible with mt2701 driver,
so the patch lets the pinctrl on mt7623 SoC reuse the driver
and deletes those redundant ones.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Acked-by: John Crispin <john@phrozen.org>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>